| Propylene is an kind of extremely important basic organic chemical raw materials. Its downstream products are numerous, and its global total capacity reaches 100 million tons per year. Traditional production methods of propylene are ethylene steam cracking and catalytic cracking. The development of the non-oil and on-purpose propylene production technologies route has been widely concerned. The coal to propylene route is very suitable for Chinese energy structure. Using natural gas, biomass, coal as raw material, methanol process has been mature and large-scale industrialized. Therefore the bottleneck of coal to propylene is methanol to propylene. In addition, it remains to be solved that the low yield, high energy consumption, high water consumption, poor mass transfer caused by impurities and environmental problems existing in coal chemical industry.Moreover, with price fluctuation of crude oil and methanol, the competition of oil route and methanol route will be fiercer. Therefore, to improve plant operation efficiency, and to reduce energy consumption for new MTO/MTP process is of vital importance. To deal with these problems, the paper firstly summarizes the existing MTP technologies, the method of process simulation and improvement. Paper then has carried on the process simulation by Aspen Plus, improved distillation sequence of refining unit, and carried on techno-economic analysis on the technical combinations.The results could be summarized as followings.(1) The sections of MTD reaction, crude separation, refinement were simulated in this paper. Based on those section simulations, the whole separation process simulation was established. Comparing with design data, simulation results were proved to be accurate and reliable. According to energy analysis results, recommendations were pointed out.(2) After simplifing refining unit of MTP process, distillation sequence problem was optimized by simulated annealing algorithm to obtain optimal separation sequence. Accroding to optimal result and actual situation, front-end depropanization separation process was proposed. Compared with front-end debutanization separation process, it possessed lower energy consumption (reduced by more than 7%), higher energy efficiency (rised by 2.1%), less CO2 emissions (reduced by 1.94* 108 kg per year), lower utilities expenses (reduced by 7%), less columns and air coolers.(3) Four technical combinations were techno-economic analyzed. By optimizing technical combinations, energy efficiency of the existing industrial process rised but its CO2 emissions reduced. In all combinations, the combination of low temperature MTD and front-end depropanization separation had the lowest energy consumption (111 tce/h) and energy cost (0.503b/y), and highest energy efficiency (0.593). Thus, it was most competitive.(4) The removal of dimethyl ether without extractive distillation was simulated. According to the result, bottom temperature of C3 splitter rised with the increase of the dry base concentration of dimethyl ether. If the dry base concentration of dimethyl ether was higher than 5000 ppm, extracting methanol must be employed. It could ensure that quench water supply enough energy for C3 splitter reboiler. It was obvious that the dosage of the extracting of methanol increased with the increase of dry base concentration of dimethyl ether.(5) Using strict simulated result form Aspen Plus, multi-objective and multi-variable optimization of MTP refining unit had been realized by NSGA-Ⅱ. The optimal parameters under design conditions were as following. Feed plate and reflux ratio of debutanizer were 11 theory plate and 0.9. Reflux flow of depropanizer and C2 splitter were 4139.892kmol/h and 420.685kmol/h. Reflux ratio of deethanizer, C3 splitter, and demethanizer were 0.906,13.572,2. |
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